The two processes most widely used for producing titanium are the Kroll process and the Hunter process.
The Kroll process reacts titanium tetrachloride, TiCl4 with molten magnesium, Mg, to produce titanium metal in an inert atmosphere, usually argon, by the reaction:2Mg+TiCl4→Ti+2MgCl2 
The Hunter process reacts titanium tetrachloride with molten sodium, Na, to produce titanium metal in an inert atmosphere, usually argon, by the reaction:4Na+TiCl4→Ti+4NaCl
Considering the atomic masses of magnesium, sodium, and titanium, the reaction equations indicate that one pound (lb.) of magnesium or 1.9 pounds (lbs.) of sodium will produce one pound of titanium. Experience has shown, however, that required magnesium and sodium quantities are 10-to-15% greater than the reaction equations suggest.
Current commercial production facilities produce titanium sponge by either the Kroll or the Hunter process. The two processes are not simultaneously or sequentially used in the same reaction vessel to produce titanium.
The reaction vessels used do not contain electrolysis cells enabling reclamation and reuse of either magnesium chloride or sodium chloride. The magnesium chloride MgCl2 and sodium chloride NaCl byproducts produced by the two processes are pumped out of the reaction vessel and transported to another site to reclaim magnesium and sodium, usually by electrolysis. The handling of molten magnesium chloride and molten sodium chloride and transportation to a remote site present technical problems which have associated costs.
U.S. Pat. Nos. 4,487,677 and 4,516,426 describe a process and equipment for production of titanium sponge which separates the magnesium chloride from the titanium immediately following the Kroll process reaction and returns the magnesium chloride to the electrolyte in an electrolysis cell inside the same reaction vessel to enable magnesium production for a succeeding Kroll process reaction.
The process described in U.S. Pat. No. 4,516,426 eliminates the need to transport magnesium chloride or sodium chloride byproducts of the Kroll and Hunter process reactions to a remote facility for reclamation of magnesium or sodium, providing potential for considerable economic benefit. Other process characteristics, however, reduce the efficiency of the process and equipment described in U.S. Pat. Nos. 4,487,677 and 4,516,426.
The electrolyte used for magnesium production is magnesium chloride; no other salts are added. This compound has a relatively high melting point of approximately 1317° F. making it necessary to operate the electrolysis cell at high temperature with concomitant short refractory life. Molten magnesium chloride has relatively low electrical conductivity, causing generation of much waste heat during electrolysis, increasing the cost of magnesium recovery.
In the process disclosed in the aforementioned patents, a fixed amount of liquid titanium tetrachloride periodically is injected into a container holding molten magnesium. This procedure did not adequately control the Kroll process reaction. Contact of liquid titanium tetrachloride which has a boiling point of 278° F. (136.4° C.) with liquid magnesium at temperatures of 1300-to-1400° F. (704-to-760° C.) followed by a highly exothermic reaction could generate high gas turbulence in the product container, blowing the magnesium pool out of the open lower end of the product container submerged in the electrolyte, preventing further titanium tetrachloride-magnesium reaction.
Very small amounts of chlorine containing more than 200 ppm water may contact steel surfaces during salt electrolysis, producing iron chloride, FeCl2. Since the compound has a melting point of approximately 1240° F., liquid iron chloride could drop into the electrolyte. Iron chloride has a lower negative free energy than magnesium chloride. Consequently, the electrolysis cell would produce iron instead of magnesium until the iron chloride had been consumed.
The container holding the titanium product produced by the Kroll process is made of graphite. Titanium carbide forms during the exothermic reaction, bonding the titanium to the product container and making titanium separation without breaking the container difficult, thus adding to the cost and difficulty of producing titanium.
U.S. Pat. No. 6,942,715 describes stirring methods to increase the efficiency of the reaction of titanium tetrachloride and magnesium in producing titanium by the Kroll process. Stirring is not used to enable this reaction in the process herein described.